How Can I Make Json.NET Throw Exceptions for Missing Fields During Deserialization?

Detecting missing fields during JSON deserialization using Json.NET

In JSON deserialization, handling missing fields is crucial. By default, Json.NET's serializer silently returns a default value when it encounters a missing field. This behavior can cause undetected errors when deserializing objects with incorrect properties.

Question:

You are encountering an issue where the Json.NET serializer does not throw an exception when deserializing an object with missing fields. Instead, it returns default values, which makes it difficult to detect incorrect data.

Solution:

Json.NET provides a configurable MissingMemberHandling setting. By setting it to Error, you instruct the serializer to raise JsonSerializationException when a missing field is encountered during deserialization. This way you can handle such errors explicitly in your code.

Code:

<code class="language-csharp">using Newtonsoft.Json;

try
{
    // 读取JSON字符串
    const string correctData = @"{ 'MyJsonInt': 42 }";
    const string wrongData = @"{ 'SomeOtherProperty': 'fbe8c20b' }";

    // 创建序列化器设置
    JsonSerializerSettings settings = new JsonSerializerSettings();
    settings.MissingMemberHandling = MissingMemberHandling.Error;

    // 反序列化对象
    var goodObj = JsonConvert.DeserializeObject<MyJsonObjView>(correctData, settings);
    Console.WriteLine(goodObj.MyJsonInt.ToString());

    var badObj = JsonConvert.DeserializeObject<MyJsonObjView>(wrongData, settings);
    Console.WriteLine(badObj.MyJsonInt.ToString());
}
catch (Exception ex)
{
    Console.WriteLine(ex.GetType().Name + ": " + ex.Message);
}</code>

Output:

<code>42
JsonSerializationException: Could not find member 'SomeOtherProperty' on object
of type 'MyJsonObjView'. Path 'SomeOtherProperty', line 3, position 33.</code>

By setting MissingMemberHandling to Error we ensure that the serializer will throw JsonSerializationException for objects with missing fields, allowing you to handle errors and ensure data integrity.

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